This application is related in subject matter to U.S. patent application Ser. No. 12/842,861, filed on Jul. 23, 2010, “Network-Based Location of Mobile Transmitters”, the subject matter of which is hereby incorporated by reference in its entirety.
Early work relating to network-based Wireless Location Systems (WLS) is described in U.S. Pat. No. 4,728,959, “Direction Finding Localization System” (issued Mar. 1, 1998) which discloses a system for locating cellular telephones using angle of arrival (AOA) techniques and U.S. Pat. No. 5,327,144, (issued Jul. 5, 1994) “Cellular Telephone Location System,” which discloses a system for locating cellular telephones using time difference of arrival (TDOA) techniques. Further enhancements of the system disclosed in the '144 patent are disclosed in U.S. Pat. No. 5,608,410, (issued Mar. 4, 1997), “System for Locating a Source of Bursty Transmissions”. Location estimation techniques for wide-band wireless communications systems were further developed in U.S. Pat. No. 6,047,192 (issued Apr. 4, 200), “Robust, Efficient Localization System”, U.S. Pat. No. 7,844,280, “Location of wideband OFDM transmitters with limited receiver bandwidth”; and Ser. No. 12/842,861, “Network-Based Location of Mobile Transmitters”.
All of these patents are assigned to TruePosition, Inc., the assignee of the present invention. TruePosition has continued to develop significant enhancements to the original inventive concepts. First commercially deployed in 1998, overlay network-based wireless location systems have been widely deployed in support of location-based services including emergency services location.
A wireless location system's performance is normally expressed as one or more circular error probabilities with a defined yield. The United States Federal Communications Commission (FCC) as part of the 2001 Enhanced 9-1-1 Phase II mandate currently (in 2011) requires that network-based systems, such as U-TDOA, be deployed to yield a precision that generates a one-hundred meter (100 m or 328.1 feet) accuracy for a yield of 67% of emergency services callers and a three-hundred meter (300 m or 984.25 feet) accuracy for a yield of 95% of emergency services callers. In 2011, the FCC set a new single location accuracy requirement, to be implemented in 2019 (for any and all E911 location technologies) to 50 meters for 67% emergency services callers and 150 meters accuracy for 95% of emergency services callers. This legal requirement makes location accuracy (and yield) of paramount importance for wireless location systems. As realized and noted in extensive prior art, the ability to routinely, reliably, and rapidly locate cellular wireless communications devices has the potential to provide significant public benefit in public safety and convenience and in commercial productivity. Similar to the United States Enhanced Wireless 9-1-1 program, the European Commission's E-Call initiative seeks to provide location-facilitated emergency assistance to motorists.
The 3rd Generation Partnership Program (3GPP) realizing that the Code Division Multiple Access (CDMA) based Universal Mobile Telephony System (UMTS) would fail to meet the International Telecommunications Union's (ITU) requirements for 4th generation cellular communications (the “IMT-Advanced” specification), launched the Orthogonal frequency-division multiplexing (OFDM) based Long Term Evolution (LTE) project and then later the LTE-Advanced project (also OFDM-based).
As an evolution of EUTRAN (aka LTE), LTE-Advanced is quite complex, with dynamic channel bandwidths, different transmission schemes for the downlink and uplink, both frequency and time domain duplexing (FDD and TDD) transmission modes, and use of multiple-input-multiple-output (MIMO) antenna techniques for both the enhanced NodeB basestation as well as at the wireless device (User Equipment (UE)).
LTE-Advanced performance targets are defined in 3GPP TR 36.814, “Further Advancements for E-UTRA Physical Layer Aspects.” Of the new features, the Enhanced uplink multiple access scheme, clustered SC-FDMA (N-times DFT-spread OFDM) will be used to increase the uplink (UE to eNB) data rate. Clustered SC-FDMA allows frequency selective scheduling within a component carrier for better throughput.
As part of the LTE and LTE-Advanced projects, “relay stations” were redefined from the well-known, simple analog signal repeaters to “relay nodes” (RN) that may adjust power control settings, use self-cancellation, decode the signal, correct errors and regenerate and then forward the received, relayed signal using another channel, modulation or frequency band.
Three RN deployment scenarios for 3GPP Release 10 are foreseen: a) outdoor relay; b) indoor relay c) thru-wall relay. These deployment scenarios are detailed in 3GPP Technical Report 36.826 V0.11.0; “Evolved Universal Terrestrial Radio Access (E-UTRA)-Relay radio transmission and reception”. The technical report (TR) that includes the 3GPP LTE-Advanced Rely node and donor cell functionality is 3rd Generation Partnership Project; Technical Report 3GPP TR 36.814—“Further advancements for E-UTRA physical layer aspects”; (Release 9) in Sections 9 and 9A. The 3GPP technical specification 36.300 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Overall description; Stage 2 (Release 10) details the interfaces for communications between Relay-eNB and Relay-UE in Section 4.7
Use of Relay Node in LTE-A allows for cell expansion, much like with traditional repeaters, and cooperative relaying where both the serving LTE-A Enhanced NodeB (eNodeB or simply eNB) radio base station and the relay node act to provide communications with the User Equipment (UE).
An eNB used with Relays is deemed a “Donor”. Relays used for cell expansion are termed “Type-I” or “non-transparent”. Cooperative Relays are termed “Type-II” or “transparent”. A Type-I (non-transparent) relay rebroadcasts the control and reference signals provided by the donor eNB and relays bidirectional data between the donor eNB and the UE. A Type-II (transparent) relay does not rebroadcast the control and reference signals and serves to relay bidirectional data between the donor eNB and the UE as to provide transmission gain and multipath diversity on the radio communications link.
The 3GPP standards also allows relay support also for legacy LTE phones (a Type-I family relay node looks to a UE as regular LTE (Release 8) eNodeB while Type-II relays in use cannot be detected by UEs).
The LTE-A model discussed below is an exemplary but not exclusive environment in which the present invention may be used.